Unidirectional antenna has been widely investigated due to its capability of confining or concentrating radiation in a desired direction. Conventionally, complementary antenna has been used to obtain a unidirectional radiation pattern.
A unidirectional radiation pattern can be broadly classified into two types: broadside radiation and lateral radiation. For broadside radiation, magneto-electric dipoles have been used in various applications including wideband, low-profile, diversity, dual-band, circular-polarization, and reconfiguration applications. On the other hand, for unilateral radiation, structures with cavity-backed slot-monopole configurations have been used.
In some applications, lateral radiation may be more preferred than the broadside radiation. For example, for a household wireless router that is arranged to be placed against a wall, a unilateral radiation pattern is more preferred because back radiation inside the wall, if any, would go wasted. Problematically, however, existing structures for unilateral radiation require the use of cavities and relatively large ground planes, and hence are rather bulky.
There is a need for a unidirectional antenna, in particular one that generates unilateral radiation pattern, that is compact, easy to manufacture, and operationally efficient, to be adapted for use in modern wireless communication systems.